Prussic Acid and Nitrates in Sorghum and Sudan Grasses: Proper Sampling for Grazing Animals

Often, Ward Laboratories, Inc receives sorghum samples and producers want us to test prussic acid and nitrates.  My recommendation would be to send two separate samples when testing for grazing purposes because prussic acid and nitrates accumulate in different parts of the plant. Prussic acid accumulatesin the leaves of the grass in contrast to nitrate which accumulates in the plants lower stock.

Prussic acid is also known as hydrogen cyanide (HCN).  The compound is present in the leaves of the plants in a compound called dhurrin.  Under normal conditions, plant membranes separate dhurrin from the enzyme responsible for hydrolyzing HCN from dhurrin. Monogastric animals and hindgut fermenters such as swine and horses, typically do not have an issue with prussic acid poisoning as stomach acid deactivates the enzyme.  However, ruminants such as cattle, sheep and goats, are more susceptible to prussic acid poisoning due to the chewing of their cud.  As those animals ruminate, the cell membranes are damaged allowing the enzyme access to dhurrin, thereby releasing HCN into the rumen.  The HCN is then absorbed directly into the bloodstream where is binds hemoglobin.  The bound hemoglobin can not transfer oxygen to individual cells and death by asphyxiation is the result.

An additional risk for prussic acid poisioning is posed by stressed and damaged plants , this is when it becomes toxic to non-ruminant livestock.  Drought stressed plants may accumulate more unbound HCN in their leaves.  Frost damaged plants also have unbound HCN in their leaves due to the frost having broken the cell membranes allowing enzyme access to dhurrin.  In the case of frost, outer cell membranes have also been damaged, therefore waiting 4-5 days before grazing is sufficient assurance that the hydrogen cyanide gas has escaped the plant leaves.  After a frost, regrowth is toxic past the 4-5 day time frame and should certainly be tested before turning animals out to graze.

So, for testing prussic acid take leaves from 20 different plants across the field for a representative sample.  Do not cut the leaves and avoid as much damage as possible.  Immediately place all leaves in a gallon sized zip lock bag. Either ship the sample overnight, or drop the sample off at Ward Laboratories, Inc. as soon as possible.  When we receive your sample, we will refrigerate it and run it as quickly as we can as to not loose any HNC and to avoid a false low value.  Samples reported at >200 ppm as received are considered toxic and allowing animals to graze would result in a rapid death toll.

I have covered nitrate toxicity in other blogs including: Do I Need to Test for Nitrates?, 6 Cautions When Grazing Cover Crops, and 4 Considerations for Feeding Hail Damaged Forage and Crop Residues. So, for testing nitrates in sorghum and sudan grasses for grazing go into the field and cut the plant at the point where you plan to pull animals off.  Then, cut 4-6 inches above that, with this small piece use plant shears and snip it into pieces.  Repeat this with 20 randomly located plants across the field.  Then mix all the small plant pieces together and take a representative sub-sample from that pile.  Place them in a zip lock bag and send them to Ward Laboratories, Inc. for nitrate analysis.

In summary, test the leaves for prussic acid and the stocks for nitrate.  It is always important to take a representative sample for the most accurate results and informed production decisions.

Additional Resource:

Nitrate and Prussic Acid Toxicity in Forage

Do I Need to Test For Nitrates?

Last week I attended both the Colorado Cattlemen’s Annual Convention and the Sandhills Ranch Expo at the Ward Laboratories Inc tradeshow booths.  At both locations, producers had concerns about nitrates.  The climate and weather however were contrasting conditions.  Colorado producers wondered how drought stress might affect the nitrate levels in their forages, while Nebraska and South Dakota producers were concerned if too much precipitation might have affect nitrate levels in forages.  Here are 5 factors that affect how nitrates accumulate in forages.

  1. Plant Species

Some plant species accumulate nitrates more than others.  These species should be tested for nitrates regularly before feeding to animals.  These species are: sorghum (milo), sudan grass, millet, oats, johnson grass, broadleaf weeds, corn and sunflowers.  There are other species which also accumulate nitrates but not to the same extent as those listed above: wheat, rye, and triticale fall into these categories.  Finally, under extreme stress alfalfa and soybeans can accumulate nitrates, however the stress must be extensive, and this situation is very rare.

  1. Maturity of the Plant

Young plants and regrowth take up nitrogen from the soil faster than it can be converted to protein.  Older more mature plants take up nitrogen at a slower rate and have had plenty of time to convert nitrogen to protein.  Therefore, younger plants and regrowth tend to accumulate more nitrates than older mature plants.

  1. Plant Part

The lower 1/3 of the stock of the plant is where the most nitrates are stored.  Leaves and stems do not store nitrates in the plant. When grazing, leaving the last third of the stock might be a good idea to avoid any nitrate toxicity issues.

  1. Environmental Conditions

Stress due to weather or climate may increase nitrate accumulation.  During drought stress, the plant may be able to take up nitrogen but not have enough moisture to convert it to protein.  On the other hand, coming out of a drought a dramatic increase in moisture may cause the plant to take up more nitrogen than it can convert to protein in a timely fashion.  Frost and freezing temperatures also cause stress to the plant and nitrate accumulation.

  1. Management

Nitrogen fertilization is a common cause of nitrate accumulation in forages.  Nitrogen fertilization may increase yield, but it also increases risk of nitrate toxicities.

Nitrates are tricky.  I often run into producers who want to tell me their situation and management practices and ask if they need to test.  The truth is no one can determine the nitrate levels based on an antidote.  Testing is the only way to have full confidence.  If there are concerns, send forage samples to Ward Laboratories, Inc for a nitrates test and use the table below as a guide to interpert your report.

Nitrates

Silage for Beef Cattle 2018 Conference

Last week I attended the Silage for Beef Cattle Conference in Mead, NE.  For those of you who put up corn silage, or provide advice for those who do I would highly recommend listening to the online uploads from this conference as well as looking over the proceedings. Here are 8 key concepts I took away from the conference:

  1. Processing is crucial.

Processing of the grain is very important to the digestibility and therefore, energy availability of the corn silage.  It is recommended that there should not be a single intact corn kernel in the final silage product.  To monitor this, separate the forage portion of the silage from the grain and then closely inspect the grain.  Adequate and consistent monitoring through the chopping process is key.

  1. Determining when to harvest is difficult and varies by operation.

As the plant matures fiber increases, kernel hardness increases thereby decreasing the digestibility of the forage and starch portions of the plant.  However, at a more immature stage less corn kernels are present, and the moisture of the plant is too high for ensiling.  Therefore, the recommendation was to harvest a week before or at black layer when the dry matter content of the green chop is between 33 – 38%.  However, the best practices may differ from operation to operation.

  1. Ensiling time is important.

As fermentation time increases, starch digestibility also increases.  For the fermentation to go to completion, it is recommended to ensile at least 90 days, but 120 days would be optimal.

  1. Packing is key to minimize shrink and prevent spoilage.

Delayed packing increases risk of yeast and mold spoilage.  It is also important to pack with enough weight and consistency.  Check out this packing density calculator from University of Wisconsin extension.

  1. Proper covering is also key to prevent shrink and spoilage.

O2 barrier plastics are the best option for covering, however polyethylene coverings are also an option with about a 5% difference in dry matter recovery.

  1. There are lots of ways ensiling can go wrong.

Silage contaminants can come from many different sources including soil, damages plants from hail or insects, manure, wildlife, rodents and birds.  These contaminants can include infectious microorganism such as salmonella, listeria, clostridia and toxin producing molds or undesirable fermentation by-products such as toxic amines or ammonia.

  1. Feeding spoiled corn silage at any inclusion rate is detrimental to rumen health.

Both dry matter intake and digestibility of neutral detergent fiber decrease when spoiled corn silage is included in the diet.  Additionally, when cannulated cattle were examined, the forage mat in the rumen was completely destroyed, again at any inclusion rate of spoiled corn silage.

  1. Producers can determine if they have aerobic deterioration of silage on farm.

At Ward Laboratories, Inc, I often suggest producers who are unsure of their silage to test both mold count and pH.  On farm producers can take the temperature of the center of the pile and other outer locations.  Moldy spots will be 20-30°F hotter, with up to 8 times the coliform forming units of mold than the core of the pile.

Again, this is a snapshot of the important information shared at the corn silage conference.  Check out the online uploads and consider sending your silage samples to Ward Laboratories Inc. to test for nutrient contents, pH, moisture and mold count.

Backyard Bird Feeders

Recently, here at Ward Laboratories, Inc., birds have been the topic of conversation.  We have had birds in nest over our doorways:

babydove
Eurasian Collared Dove

birds in nests in surrounding trees:

babyrobin
Robin

and even birds in the ceiling!

bird in ceiling
Starling in the Ceiling

Additionally, being located in Kearney, NE, we see our fair share of avid bird watchers who are drawn to the area to view over half a million Sandhill Cranes that stop here in the Platte River Valley to refuel along their spring migration.  So, with all this talk about birds, of course I thought I should share our testing of bird food.

If you supply bird food to your backyard feathered friends, you have probably noticed there is a guaranteed analysis provided on each bag.  Commercial bird feed formulations are required to set minimum crude protein, minimum crude fat and maximum crude fiber levels.  Here at Ward Laboratories, INC., we test bird feed so the manufacturer can  ensure they are meeting set standards for each seed type or mixed feed.

 

birdseed
Bird Seeds 

Forage Creativity: Soy-Corn Silage

Here at Ward Laboratories Inc., we often encourage producers to be creative and try newapproaches to agricultural production.  A couple of weeks ago at the American Society of Animal Science Midwest meeting in Omaha, I listened to a talk about getting more creative with corn silage: “Production of High-Quality Forage through Unique Forage Blends” presented by Dr. Ishwary Acharya.  Ward Laboratories Inc. tested 1,451 corn silage samples and 2,197 total silage samples of all types in 2016.  So, I have seen the range and variation in the nutrient quality of silages used in the area.  Dr. Acharya’s research focused on making the best possible silage for a dairy operation, as he stated in his talk, “the ultimate measure of forage quality is milk production”.  Being in central Nebraska, I think his research could not only increase the nutritional content of the silages produced, but also the value of grazing the cornstalks by a beef enterprise after harvest.

The idea behind Dr. Acharya’s presentation was to double crop corn and vining soybeans to produce high protein low fiber silage without sacrificing yield.  First, to produce the best possible corn silage, the crop was chopped higher than producers typically chop corn silage.  This resulted in less stock and more leaves, husks, and cob in the silage.  Therefore, yield was compromised for higher protein and lower fiber concentrations.  The second part of the presentation explained that to overcome the sacrifice of yield, vining soybeans could be intercropped with the corn.  Therefore, when chopping for silage at a higher level, the soybean plant material made up for the loss of stocks in the yield.  In this study, the resulting silage had increase yield, forage quality, and protein compared with typical corn silage.  Dr. Acharya interseeded the vining soybean at various rates and determined that the optimal rate was somewhere between 67% corn 33% soybeans and a 50:50 mix.  The study also looked at the optimal time for fermentation based on pH and presence of volatile compounds that have affect on rumen function and animal performance.  At 60 days of fermentation Dr. Acharya determined that fermentation had not gone to completion and the silage should be ensiled for at least a 90-day period.  This finding agrees with other literature I have read on the topic.

Dr. Acharya’s idea of double cropping to create a high-quality forage source for dairy cattle could also be of benefit to beef cow calf pairs grazing the remaining corn stalks.  If soybeans were intercropped, I would predict that there would be some beans and vining materials left in the field which would be higher in protein and lower in fiber than the corn stalks alone.  Of course, I would advocate that producers test both their silage and try to get a representative idea of what has been left on their field to provide necessary supplementation.  For the silage, I would recommend testing crude protein, acid detergent fiber to predict energy values and neutral detergent fiber to predict dry matter intakes at a minimum noting that the sample would need to be ran as a wet chemistry feed test and that the addition of soybean to the silage would not allow for a reliable and accurate NIR scan.  For the grazing stocks and soybeans, I would run the same test to get an idea if protein or energy supplementation are necessary.  I would also caution that soybeans do contain urease and we typically do not graze cattle on soybeans fields as they risk urease toxicity if they have recently consumed non-protein nitrogen (NPN), therefore when considering supplementation strategies for cattle grazing a field of cornstalks intercropped with vining soybeans, lick tubs or mineral mixes with urea could not be utilized.

As, with any novel feed, always monitor animal body condition, production and health to ensure it is providing the nutrients required.  Don’t be afraid to try something new.  It might be of benefit to your operation weather it is vining soybean corn silage or grazing cover crops or feeding from the waste stream, feed testing and good ration and diet formulation can lead to success of a livestock operation.

Feeding Wild Animals

Intermittently, I receive a phone call asking me about the interpretation of a feed analysis for a wild animal as opposed to domesticated livestock whose nutrient requirements I am more familiar with.  These phone calls usually make me do a little more research and I learn something new about animal nutrition with each inquiry.

The first time this happened, I was new to consulting here at Ward Laboratories, INC.  A producer called asking why his pheasants were suddenly losing their feathers and then dying.  The situation was dire, and his story was quite startling.  As it turned out, he was offered a very good deal on some wheat grain and had decided that would be the feed source for his pheasants.  Luckily for me the nutrient requirements for pheasants are listed in the National Research Council’s Nutrient Requirements of Poultry, so I was able to make a direct comparison between the grain he was feeding and the bird’s requirements.   It turned out that wheat grain was very high in energy, however much lower than the protein, and mineral requirements of ring neck pheasants.  The moral of that story was to have a solid understanding of the nutrient requirements of the animal you are feeding along with knowledge of the nutrients the feed is providing.

A common wild animal I get asked about is deer.  Most of these questions are about supplemental feed for deer for hunting purposes.  Deer are unique in because antler growth is very important to hunters.  For optimal antler growth deer have a very high requirement for protein.  It is recommended that a supplemental feed be greater than 16% crude protein.  Deer are also browsing animals not grazing animals meaning that they select the most nutritious portions of plants for consumption.  So, it has been shown that the total diet of a deer in the wild can be between 20-24% crude protein.  A lot of livestock producers want to utilize leftover feed supplements to feed deer on their property.  These supplements were formulated for livestock species consuming roughages not wild browse therefore, those feeds may cause health issues for deer.  Sheep and goat feed is low in copper and other important minerals and may cause a deficiency for deer.  Horse supplemental feeds are typically for active horses and therefore high in starch which may result in acidosis when consumed by a deer.

Most recently, I was asked about feeding bison.  Being unfamiliar with nutritional requirements of bison, I did a little research.  Nutrient requirements of bison have not been studied as extensively and are not as well defined as beef cattle.  Bison are more efficient utilizers of fiber than beef cattle.  They prefer to consume large amounts of grass to smaller amounts of legumes.  For the most efficient finishing production bison should be provided with a diet at about 14% crude protein and 70-90% concentrate diet so that energy does not limit growth.   Crude protein requirements for bison at other stages are not well defined but are thought to be just below those for productive beef cattle.  This is because nitrogen recycling is more prevalent in these wild ruminants than in cattle.  A management challenge bison producers face is the sensitivity of bison to cool temperatures and shorter photoperiods.  Instinctually, these animals conserve energy during the winter and consume less feed, gain less and are less productive in the winter months.  However, during summer months, bison consume more feed, gain weight at a quicker rate and are more productive.

When feeding wild animals, be sure to do some research and familiarize yourself with that animal’s nutrient requirements, as well as common feeding practices by other producers or game promoters.  Then be sure you understand the feed ingredients and how they are going to meet those nutritional requirements. Ward Laboratories Inc. can test your feeds to get an accurate report of the nutritents in the feeds you are supplementing and I am here as a consultant to help you research the nutritnet requirements of different animals.   After meticulously formulating a diet or supplement, monitor the animals you are feeding to ensure they are healthy and productive.

Drought Planning: 4 Ways to Stockpile Forages

The state of Nebraska is in the center of the High Plains Region of the United States.  The states that make up this region are Nebraska, Kansas, Colorado, Wyoming, and the Dakotas.  I checked the current drought monitor and found that southern Nebraska and southern Wyoming are abnormally dry, and Kansas, Colorado and the Dakotas are experiencing various levels of drought.  The current outlook through April is promising for the Dakotas, but dry for the rest of the region.  Precipitation from the Canadian border is predicted to remove the drought from North and South Dakota. The Dakotas are projected to experience a normal spring season.  As for the rest of the region, southern Nebraska, southern Wyoming, Colorado and Kansas, drought is likely to persist through April 1st.  Soil moisture levels on April 1st will have a great impact on the availability of forages throughout the region during the summer months. When planning for drought conditions, which are likely to result in decreased forage production, especially on dry pastures and rangeland, most producers’ strategy is to decrease animal numbers and stockpile forages.  Here are four ways to stockpile forages for livestock during drought conditions:

  1. Buy Hay

Buying hay is the first thing that usually comes to mind when people think of stockpiling forages.  During a drought, it is likely that local hay may be of lower quality, therefore it is important to test the protein and energy values (I reccomend a minimum of an NIR scan or the F-3 test at Ward Laboratories, Inc.) before feeding to ensure the forage will meet the animals’ nutritional needs. Hay nutrient values may change during transportation, so if hay is being shipped from another region be sure to test after receiving the lot and before balancing a ration to feed livestock.  Having extra stockpiles of hay for drought or emergency feeding is never a bad thing, however buying hay during a drought can be expensive due to less availability, higher demand, and transport costs.  Therefore, it would be beneficial to maintain supplies of hay during periods of plentiful forage conditions. In other words, it is most economical to buy hay in excess when it is low in demand and forages are in good supply and save some back as emergency or drought feed.  If you are located in Nebraska and are looking to buy hay check out the Nebraska State Hay Hotline.

  1. Graze Crop Residues

If your operation is located near farmland, consider working with your neighbors to allow your livestock to graze their crop residues.  Cattle can graze preferentially to take advantage of high protein, low fiber portions of the plants left standing in the field.  If you reside in southern Nebraska or Kansas, corn or wheat residues are good alternative forages especially when fed with energy supplements.  When grazing crop residues, be cautious and remember to test for nitrates before letting animals out onto the filed.  This option for stockpiling forages is cost effective, however labor intensive and may require cooperation with neighbors.  If you live in Nebraska check out the crop residue exchange to find farmers willing to let you take advantage of this great forage source.

  1. Graze Cover Crops

Adding cover crops to your own cropping rotation can be another great way to stockpile forages.  Cover crops allow you to extend the grazing season into the fall.  Preferential grazing increases the animals nutritional plane and therefore performance may also increase.  If you are lucky enough to get some moisture after grazing, cover crops may produce regrowth and animals may be able to graze those areas again.  There are also many benefits to adding cover crops into a cropping rotation for the soil. For more information on that read guest author, Emily Shafto’s Cattle and Crops: Completing the Nutrient Cycle. Planting a diverse cover crop mixture can ensure that if one species in the mix fails others will thrive, diversity can prevent disaster. Cover crops are cost effective as a source of forage, especially in a drought.  They are however, more labor intensive and if they are high in nitrates, prussic acid or sulfur, they may detrimentally affect animal health and mortality.

  1. Rent Additional Grazing Lands

If you are not located in an area where cropping agriculture is prevalent, and you rely on rangelands to provide forage for the summer grazing months.  Renting additional grazing lands may not be very cost effective immediately, but in the long run it will take some of the pressure off the lands typically grazed and allow them to rest and rejuvenate to provide forage for the next grazing season.  Renting additional grazing lands may be a hit to the pocketbook during that drought season, but it will prevent over-grazing, which is a necessity when practicing good land stewardship.

 

Stockpiling forages, using one or more of the strategies above, can help prevent a disastrous drought situation.  Always monitor the precipitation and temperature conditions so that you can do your best planning for the future.  Always look for creative ways to fill gaps in feed availability.  A feed or NIR test from WARD Laboratories, INC can aid in decision making when it comes to feeding alternate forages. When buying hay, test nutritional values after shipment and before feeding for accurate results.  When grazing corn stalks, oat stubble or wheat stubble check for nitrates before letting animals out in the field.  And revisit my blog 6 Cautions When Grazing Cover Crops to ensure you are feeding a safe forage when grazing cover crops.  For more information on drought planning visit the National Drought Mitigation Center.

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